import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Scanner;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: 28779
 * Date: 2023-11-26
 * Time: 17:44
 */
public class TcpEchoServer {
    public ServerSocket serverSocket  = null;
    private ExecutorService service = Executors.newCachedThreadPool();

    public TcpEchoServer(int port) throws IOException {
        serverSocket  = new ServerSocket(port);
    }

    public void start() throws IOException {
        System.out.println("服务器启动！");
        while (true) {
            Socket clientSocket  = serverSocket .accept();

            //使用线程池
            service.submit(new Runnable() {
                @Override
                public void run() {
                    processConnection(clientSocket);
                }
            });
        }
    }

    private void processConnection(Socket clientSocket) {
        System.out.printf("[%s:%d] 客户端上线!!\n", clientSocket.getInetAddress().toString(), clientSocket.getPort());

        try (InputStream inputStream = clientSocket.getInputStream();
             OutputStream outputStream = clientSocket.getOutputStream()){

            while (true) {
                Scanner scanner = new Scanner(inputStream);

                if(!scanner.hasNext()) {
                    //服务器下线
                    System.out.printf("[%s:%d] 客户端下线!!\n", clientSocket.getInetAddress().toString(), clientSocket.getPort());
                    break;
                }

                String request = scanner.next();

                String response = process(request);

                PrintWriter writer = new PrintWriter(outputStream);
                //    使用 PrintWriter 的 println 方法, 把响应返回给客户端.
                //    此处用 println, 而不是 print 就是为了在结尾加上 \n . 方便客户端读取响应, 使用 scanner.next 读取.
                writer.println(response);

                //刷新缓冲区
                writer.flush();

                // 日志, 打印当前的请求详情.
                System.out.printf("[%s:%d] req: %s, resp: %s\n", clientSocket.getInetAddress().toString(), clientSocket.getPort()
                                    , request, response);
                System.out.println(outputStream);

            }

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                clientSocket.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        TcpEchoServer server = new TcpEchoServer(9090);
        server.start();
    }
}
